Linux Kernel EUVD-2025-209747

The vulnerability resides in the Direct Rendering Manager (DRM) subsystem's shared memory (shmem) helper functions, specifically within test code (drm/tests/drm_gem_shmem_test.c). The DRM graphics subsystem uses reservation locks to synchronize access to GEM (Graphics Execution Manager) objects in memory. The madvise operation, when called on shmem objects via drm_gem_shmem_madvise_locked(), requires that the reservation lock be held to prevent concurrent access violations. The test code was invoking this locked variant without acquiring the lock first, leading to kernel warnings logged at drivers/gpu/drm/drm_gem_shmem_helper.c:499. CWE classification not provided, but this is fundamentally a synchronization/locking issue (conceptually similar to CWE-667: Improper Locking). The fix exports a new helper function drm_gem_shmem_madvise() that wraps the locked operation with proper lock acquisition and release for test use only.